1. Field of the Invention
This invention relates to an original image reading device, and more particularly, to an original image reading device which includes means for detecting the density of a sheet fed by an automatic sheet feeder.
2. Description of the Related Art
Heretofore, in performing automatic density adjustment when copying a sheet using an automatic sheet feeder, the density of the sheet has been detected by density detection means provided within the main body of an image forming apparatus, and a signal representing the density has been transmitted to the main body of the image forming apparatus to perform automatic density adjustment.
In the above-described prior art, however, since density detection is performed after mounting the sheet on a platen glass of the image forming apparatus using the automatic sheet feeder and density adjustment is performed after receiving the detection signal, a considerable amount of time is needed before starting a copying operation. As a result, the prior art has the problem that the number of sheets which can be copied within a unit time by the image forming apparatus is reduced.
A plurality of sheet feed paths are present in the automatic sheet feeder, such as a path to feed the sheet to a predetermined position in the image forming apparatus, a path to reverse the sheet, a feed path for manually providing a sheet in an interrupt operation, and the like. If density detection means are provided at the plurality of paths, additional time is needed for adjusting the density levels of the respective detection means with one another, and problems might occur as a result of insufficient adjustment. Furthermore, the prior art, for example, might have the problems that the size of the apparatus becomes large as a result of providing a large number of detection means, and the production cost is thereby increased.